The present invention relates to a lamp sockets, and relates more particularly to an improved structure of lamp socket which is easy to assemble and safe in use.
Various decorative strings and Christmas tree light sets are well-known and intensively used in western countries as well as most Asian countries during Christmas holidays. When installed, decorative strings and Christmas tree light sets are controlled to flash and to give different colors of light. The lamp socket for a decorative string or Christmas tree light set generally comprises a socket shell having a positive contact metal plate and a negative contact metal plate, a socket cap fastened to the socket shell to hold down an electrical wire causing the positive and negative contact metal plates respectively pierced into the insulator of the electrical wire and made a respective electrical contact with either conductor of the electrical wire. The positive contact metal plate has a vertical front end inserted through a hole on the top wall of the socket shell and pierced through the insulator of the electrical wire and made an electrical contact with the respective conductor of the electrical wire, and a horizontal rear end disposed inside the socket shell below an inside projecting portion on the top wall of the socket shell. When the base of the lamp bulb is threaded into the socket shell, the ring contact and tip contact of the lamp bulb contact the negative and positive contact metal plates respectively. Under normal condition, the horizontal rear end of the positive contact metal plate is spaced from the projecting portion on the top wall of the socket shell, and therefore it contacts the tip contact of the lamp bulb when the lamp bulb is threaded into the socket shell. When the lamp bulb is threaded into the socket shell, the tip contact of the lamp bulb is spaced from the projecting portion on the top wall of the socket shell at a distance longer than the thickness of the horizontal rear end of the positive contact metal plate. However, the positive contact metal plate tends to cause an elastic fatigue after long uses. Therefore, a contact error happens when the horizontal rear end of the positive contact metal plate is disposed constantly in contact with the projecting portion of the top wall of the socket shell.